If you are looking to ship a package to its destination within a period of 3 days, then the best option available to you with any provider is priority shipping. Delivery times for this service are about the same as most providers. However, the good news is that with priority shipping, you can avail some of the lowest rates, provided your package weighs under a certain unit. This bar goes up and down with the provider, but the differences aren’t staggering. So, if you want to avail the most competitive rates, your packages have to weigh less.